12 research outputs found
Temperature evolution of dielectric characteristics of PVDF and P(VDF-TrFE) films produced by 4D printing
No full textIn this work, films of polyvinylidene fluoride, copolymer of vinylidene fluoride and trifluoroethylene have been studied. The samples were made by direct ink writing technology. Some of the produced films were polarized in the corona discharge field. The dependences of the relative permittivity on temperature were studied for the films. The study showed that for polyvinylidene fluoride films, no maximum is observed in the dependences of the permittivity on temperature, since the assumed temperature of the ferroelectric phase transition is higher than the melting temperature. The maximum in the temperature dependence of permittivity for polarized copolymer of vinylidene fluoride and trifluoroethylene films is shifted by 10℃ toward higher temperatures compared to the maximum for non-polarized films. In this case, the permittivity of non-polarized films has higher values compared to the corresponding value for polarized samples. This is due to an increase in the proportion of the β-phase after polarization, as well as to the internal electric field caused by the space charge formed during the polarization process at the phase boundaries
Electrical response of lithium niobate and lithium tantalate thin films to modulated thermal radiation
No full textIn this work, we studied the pyroelectric activity of thin polycrystalline lithium niobate films fabricated by radio frequency magnetron sputtering and laser ablation, and thin polycrystalline lithium tantalate films fabricated by radio frequency magnetron sputtering. Using the dynamic method of studying the pyroelectric effect, it was found that all samples have self-polarization that occurs during the post-growth thermal annealing of the structure. An estimate of the pyroelectric coefficient showed that the values of the pyroelectric coefficient of lithium niobate and lithium tantalate thin films are several times lower than the values of the pyroelectric coefficient for bulk crystals of the corresponding materials. This may be due to the fact that the polarization vector of some grains lies in the film plane, as well as to the traps existing in the film volume and at the film/substrate interface, on which charge carriers recombine and do not participate in the generation of the pyroelectric current
Experimental studies of the medical radioisotopes production in neutron spectra generated by 660 MeV protons and 1-8 GeV deuterons in massive uranium target
No full textTemperature dependence of the pyro- and photoelectric response in Sn/sub 2/P/sub 2/S/sub 6/ films
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Multilayered ceramic heterostructures of lead zirconate titanate and nickel-zinc ferrite for magnetoelectric sensor elements
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Исследование сегнетоэлектрических нанокомпозитов на основе P(VDF-TrFE) методами сканирующей зондовой микроскопии
Get PDFCeramic and polymer based nanocomponents combine the properties of their constituents, e.g. flexibility, elasticity, polymer reprocessability, hardness typical of glass, wear resistance and high light refraction index. This helps improving many properties of the materials in comparison with the source components. Since recently researchers have been manifesting interest to the properties of complex composite compounds. This is primarily caused by the unique properties of their structures as compared with conventional materials having homogeneous composition. Secondly, this interest is caused by the fact that these compounds may prove to be much cheaper than homogeneous structures provided the physical properties of the composite in a preset range of parameters (temperature, applied field frequency etc.) are identical to those of the respective homogeneous materials. For example, polyvinyl idenfluoride (PVDF) type ferroelectric polymers and copolymers on its basis have found wide application for functional elements of various electromechanic devices in advanced electronics due to their relatively good piezoelectric and pyroelectric properties. The strong random polarization and the formation of polar non-centrosymmetric crystals provide for the high piezoelectric and pyroelectric activity in these crystals. Scanning probe microscopy has been used for study of ferroelectric nanocomposites having different compositions. The matrix specimen for study of local polarization switching at a nanoscale level was vinyl idenfluoride and trifluoroethylene P(VDF-TrFE) copolymer possessing sufficiently high crystallinity. The composite fillers were barium titanate BaTiO3 and deuterized triglycinsulfate DTGS ferroelectric powders and zirconate-titanate lead barium BPZT ceramic powder. We show these materials to show good promise for use in memory cells.Нанокомпозиты на основе керамики и полимеров сочетают в себе качества составляющих их компонентов: гибкость, упругость, перерабатываемость полимеров и характерные для стекол твердость, устойчивость к износу, высокий показатель светопреломления. Благодаря этому улучшаются многие свойства материалов по сравнению с исходными компонентами. В последнее время исследователи проявляют большой интерес к изучению свойств сложных композитных соединений. Во-первых, это связано с уникальными свойствами таких структур по сравнению с «обычными», однородными по составу веществами. Во-вторых, — с тем, что подобные соединения могут оказаться значительно более дешевыми, чем однородные структуры, при условии, что композит по ряду физических показателей и в диапазоне заданных параметров (температуры, частоты приложенного поля и т.д.) идентичен однородным веществам. Так, сегнетоэлектрические полимеры типа поливинилиденфторида (PVDF) и сополимеры на его основе нашли широкое применение в качестве функциональных элементов различных электротехнических устройств в современной электронике за счет своих относительно высоких пьезоэлектрических и пироэлектрических свойств. Высокая спонтанная поляризация и образование полярных нецентросимметричных кристаллов обуславливают появление в этих материалах высокой пьезо- и пироактивности. Методами сканирующей зондовой микроскопии исследованы сегнетоэлектрические нанокомпозиты различных составов. В качестве образца-матрицы для исследования локального переключения поляризации на наномасштабе был выбран сополимер винилиденфторида с трифторэтиленом P(VDF-TrFE), обладающий достаточно высокой долей кристалличности. В качестве наполнителя для композита выбраны порошки сегнетоэлектриков титаната бария BaTiO3 и дейтерированного триглицинсульфата DTGS, керамический порошок цирконата-титаната бария свинца BPZT. Показано, что эти материалы являются перспективными для использования в качестве элементов памяти.
Electron emission from ferroelectric thin films enhanced by the presence of ferroelectric domains
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